Mysterious dark energy is spread evenly across the cosmos

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The anti-gravity force that is driving the accelerating expansion of the universe appears to be distributed uniformly across space and time.

X-ray (top) and optical pseudo-color (below) images of three low-mass galaxy clusters studied by the eROSITA instrument. The highest-redshift cluster comes from a time when the universe was approximately 10 billion years younger than it is today. The cluster galaxies in that case are clearly much redder than the galaxies in the other two clusters.
X-ray (top) and optical pseudo-color (below) images of three low-mass galaxy clusters studied by the eROSITA instrument. The highest-redshift cluster comes from a time when the universe was approximately 10 billion years younger than it is today. The cluster galaxies in that case are clearly much redder than the galaxies in the other two clusters. (Image credit: eROSITA collaboration)

Dark energy, the mysterious force apparently driving the accelerating expansion of the universe, is spread evenly through space and time, new results suggest.

The findings also better constrain how much of the universe's energy and matter content dark energy accounts for, the study team said. 

They reached their conclusions after analyzing observations of galaxy clusters made by the eROSITA X-ray instrument, which searches the entire sky over Earth for these find-to-find collections of galaxies. eROSITA is mounted on Spektr-RG, a Russian-German space telescope that launched to Earth orbit in 2019.

Related: Dark matter and dark energy: The mystery explained (infographic)

Galaxy clusters are useful for understanding dark energy because, on large scales, this odd repellant "anti-gravity" force should suppress the formation of enormous cosmic structures. That means dark energy determines how and where galaxy clusters, the largest objects in the universe, can form. 

"We can learn a great deal about the nature of dark energy by counting the number of galaxy clusters formed in the universe as a function of time," study co-author Matthias Klein, an astrophysicist at Ludwig-Maximillians-Universitat Munchen in Germany (LMU), said in a statement.

The eROSITA Final Equatorial-Depth Survey (eFEDS) found about 500 galaxy clusters, one of the largest samples of low-mass galaxy clusters discovered to date. The observed clusters cover roughly the past 10 billion years of the 13.8 billion-year-old universe's evolution.

The study team combined the eROSITA observations with optical data from the Hyper Suprime-Cam Subaru Strategic Program. This enabled the first cosmological study performed using galaxy clusters detected by eROSITA.

The results of the study were then compared to theoretical predictions, confirming that dark energy accounts for around 76% of the total energy density of the universe. The findings also suggest that this energy density is uniform in space and constant in time. 

The team's results agree well with other independent approaches to the investigation of dark energy, such as previous galaxy cluster studies as well as those using an effect of gravity on light called weak gravitational lensing. Yet, while the new findings shed more light on dark energy, this force remains a mystery that physicists are eager to get to the bottom of. 

Why is dark energy so problematic?

In the 1920s, American astronomer Edwin Hubble made observations of distant galaxies that showed they are receding from us. In addition, the farther away a galaxy lies, the quicker it's moving away, which led scientists to discover that the universe is expanding.

This was shocking enough, overturning the commonly held idea at the time that the universe existed in a stable steady state. Things got weirder in 1998, when observations of distant supernovas showed that, not only is the universe expanding, but this expansion is accelerating. 

"To explain this acceleration, we need a source, and we refer to this source as 'dark energy,' which provides a sort of 'anti-gravity' to speed up cosmic expansion," said study co-author Joe Mohr, an LMU astrophysicist.

Yet, despite knowing what dark energy does and being able to calculate that it comprises around 76% of the energy and matter in the universe, scientists still are in the dark about what it actually is, or why it started acting on the universe in its later epochs.

The effect of dark energy causing accelerating expansion in the later universe, after the initial rapid expansion of the universe as a result of the Big Bang ended, is something like applying an initial push to a child on a swing. As the child slows toward a halt, the swing starts to pick up speed again, without any further push. Not only that, but it accelerates faster and faster and reaches increasingly greater heights. 

Just like the swing analogy, the accelerating expansion of the universe tells scientists that something is missing from their picture of the cosmos. 

RELATED STORIES:

— What is the Big Bang theory?

— Dark energy remains a mystery as Einstein's theory of gravity passes another test

— Black holes may be the source of mysterious dark energy

"Although the current errors on the dark energy constraints are still larger than we would wish, this research employs a sample from eFEDS that, after all, occupies an area less than 1% of the full sky," added Mohr. "The nature of dark energy has become the next Nobel Prize-winning problem."

The team's research was published last month in the journal Monthly Notices of the Royal Astronomical Society.

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Robert Lea
Robert Lea
Senior Writer

Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.

15 Comments Comment from the forums
  • mbee1
    More malarkey pretending to be knowledge. Dark matter and dark energy are math constructs, nobody has ever been able to verify either. The counting of clusters does not actually prove anything especially as they have a hole of about a third in the data, 3 billion years worth of hole. 500 clusters in a volume of space with an estimated diameter of 93 billion light years is a very low number. All that is a math construct based on background radiation assumed to have been lowered in frequency as space expanded. Nobody has actually found proof of what gravity is either. The Cern claims are just that claims. The whole expansion of space idea is simply a math construct, nobody actually knows it that is true either. You cannot see to the other side to see if there is another side. The big boom construct requires a force to expand space and hence the search for dark energy and due to some limited data on relative star movements dark matter if one simply ignores dark holes which may or may not radiate themselves away, nobody knows that either. If one assumes they do not than the number of black holes may be pretty large. None luminous matter may be much larger than known as well. Most of what passes for knowledge is actually educated guesses with nice math ribbons which may or may not be true. My point is take it all with a grain of salt and wonder at how it all came to be.
    Reply
  • rod
    I note from the paper or reference cited.

    Cosmological constraints from galaxy clusters and groups in the eROSITA final equatorial depth survey, https://academic.oup.com/mnras/article-abstract/522/2/1601/7110415?redirectedFrom=fulltext&login=false
    "ABSTRACT We present the first cosmological study of a sample of eROSITA clusters, which were identified in the eROSITA Final Equatorial Depth Survey (eFEDS). In a joint selection on X-ray and optical observables, the sample contains 455 clusters within a redshift range of 0.1 < z < 1.2, of which 177 systems are covered by the public data from the Hyper Suprime-Cam (HSC) survey that enables uniform weak-lensing cluster mass constraints..."

    The redshift of 1.2 using cosmology calculators; the age at redshift 5.173 Gyr, look back time distance 8.549 Gyr (more than 8 billion light years from Earth) and the comoving radial distance 12.462 Gly where space expands about 88% c velocity. Ref - https://lambda.gsfc.nasa.gov/toolbox/calculators.html
    The size of the universe for 1.2 redshift is < 12 Gly across. The radius as seen from Earth = 5.6644 Gly. Some neat calculations featuring many changes in the expanding universe model :) So far, I have yet to read a definitive statement on when dark energy is created in the BB model. Planck time, Planck length, inflation period, post-inflation?
    Reply
  • Ryan F. Mercer
    mbee1 said:
    More malarkey pretending to be knowledge. Dark matter and dark energy are math constructs, nobody has ever been able to verify either. The counting of clusters does not actually prove anything especially as they have a hole of about a third in the data, 3 billion years worth of hole. 500 clusters in a volume of space with an estimated diameter of 93 billion light years is a very low number. All that is a math construct based on background radiation assumed to have been lowered in frequency as space expanded. Nobody has actually found proof of what gravity is either. The Cern claims are just that claims. The whole expansion of space idea is simply a math construct, nobody actually knows it that is true either. You cannot see to the other side to see if there is another side. The big boom construct requires a force to expand space and hence the search for dark energy and due to some limited data on relative star movements dark matter if one simply ignores dark holes which may or may not radiate themselves away, nobody knows that either. If one assumes they do not than the number of black holes may be pretty large. None luminous matter may be much larger than known as well. Most of what passes for knowledge is actually educated guesses with nice math ribbons which may or may not be true. My point is take it all with a grain of salt and wonder at how it all came to be.
    You sound remarkably unknowledgeable about the scientific subject matter and the many empirical studies and experiments that underpin it. But you do you.
    Reply
  • Atlan0001
    The infinite state is always the non-local, the non-relative, state of the universe. From it to the local-relative finite state is the accelerative state. And all that would show of the infinite state, in the local-relative finite state, would be a physic of "potential" for expanding to the infinite state. Being the "set" of the gravitational state, the pointers point to it, which is to say the pointers point to the collapsed constant (the cosmological constant /\) of distant Horizon, not to the any of the constituency of the "set." I just wish they wouldn't call that rim-body of constantly opposed gravity (G), "anti-gravity." It isn't anti-gravity . . . anti-gravity is "zero-g," as in "Lagrange points."

    You can almost feel the establishment's pure hatred and total dismissal of non-local, non-relative, collapsed Horizon "set" of universe horizons of "infinity" (infinities of universes). There are physics to it. There is forever continuing working historical 'Memory' to that Horizon of infinity in which the universe forgets, all the infinities of universes (the multiverse) forget, nothing . . . including a working eternal youth in horizon.

    The gravity is contractive-expansive in equal proportions, expanding / contracting, going "nowhere" into "nothingness," which cancels out, zeros-out, resulting in anti-gravity zero-g steady state between the two other states. The two sides of the coin. We witness a multi-dimensional multiverse universe.
    Reply
  • Adoni Yannop
    mbee1 said:
    More malarkey pretending to be knowledge. Dark matter and dark energy are math constructs, nobody has ever been able to verify either. The counting of clusters does not actually prove anything especially as they have a hole of about a third in the data, 3 billion years worth of hole. 500 clusters in a volume of space with an estimated diameter of 93 billion light years is a very low number. All that is a math construct based on background radiation assumed to have been lowered in frequency as space expanded. Nobody has actually found proof of what gravity is either. The Cern claims are just that claims. The whole expansion of space idea is simply a math construct, nobody actually knows it that is true either. You cannot see to the other side to see if there is another side. The big boom construct requires a force to expand space and hence the search for dark energy and due to some limited data on relative star movements dark matter if one simply ignores dark holes which may or may not radiate themselves away, nobody knows that either. If one assumes they do not than the number of black holes may be pretty large. None luminous matter may be much larger than known as well. Most of what passes for knowledge is actually educated guesses with nice math ribbons which may or may not be true. My point is take it all with a grain of salt and wonder at how it all came to be.
    Examples Of Oxymorons In Literature And Science):
    Jumbo Shrimp): The Word “Jumbo” Means Large, While “Shrimp” Means Small!!
    In Modern Cosmology): The Galaxies Are Given As Physically Standing Still As The Space Between The Given Physically Standing Still Galaxies Expands “Actually” At Superluminal Speeds!! The Given): Lack Of Movement Between Any Two Galaxies Is, Also, Given As Simultaneous Separation Between The Two Galaxies!!
    Deafening Silence): The Word “Deafening” Means Loud, While “Silence” Means Quiet!!
    Reply
  • Unclear Engineer
    Not clear to me what "evenly across the cosmos" really means.

    First, I note that the conclusion is based on apparent fitting of simulations to observations, by varying the assumptions in the simulations to get the best fit. So, basically, this fit only can be logically applied to conclusions about matter on the scale of the observations.

    That really doesn't help address the questions about whether our solar system, our meter sticks, and even the atoms in our bodies are expanding due to the effects of "dark energy".

    And it is not clear what is meant by "uniform in time" for the dark energy distribution. I have read elsewhere that the energy density of dark matter appears to be constant with time, at least back to the creation of the CMBR. But, that would mean that the total amount of "dark energy" is actually increasing as the universe expands - and has increased by a factor of about 1,300,000,000 since CMBR creation.

    Also, this statement about the expansion of the universe "accelerating" seems to have different meanings to different writers. On the one hand, some point out that, as matter gets farther from us, in order to follow Hubble's Law, it must keep moving away faster than when it was closer to us - and that is called an "accelerating expansion". But, on the other hand, I have read that the rate of acceleration is diminished by gravitational attraction, such that the overall effect could be considered "decrease in expansion rate with time" for the universe as a whole.
    Reply
  • Atlan0001
    Unclear Engineer said:
    Also, this statement about the expansion of the universe "accelerating" seems to have different meanings to different writers. On the one hand, some point out that, as matter gets farther from us, in order to follow Hubble's Law, it must keep moving away faster than when it was closer to us - and that is called an "accelerating expansion". But, on the other hand, I have read that the rate of acceleration is diminished by gravitational attraction, such that the overall effect could be considered "decrease in expansion rate with time" for the universe as a whole.
    The expansion acceleration rate is speeding up. Toward what?! Toward the speed of light? Einstein made that trip in his mind's eye. What he found when he arrived there was 0-point and T=0, t=0. He was very late to the game, though. The ancients made that mind's eye realization thousands of years ago, saying that that is where we live, a circling, more recently a twisting circle into itself that looks like the symbol of infinity. Stephen Hawking agreed with them when he described his "Grand Central Station" of the universe (the ever-"turning unity"), with its frozen clock of time hanging in its center. All of them in fact describing the same thing in their different ways.

    Dare I say it. The absolutely perfect definition and description of an evenly spread, uniform, "perpetual motion machine."
    Reply
  • Adoni Yannop
    Atlan0001 said:
    The expansion acceleration rate is speeding up. Toward what?! Toward the speed of light? Einstein made that trip in his mind's eye. What he found when he arrived there was 0-point and T=0, t=0. He was very late to the game, though. The ancients made that mind's eye realization thousands of years ago, saying that that is where we live, a circling, more recently a twisting circle into itself that looks like the symbol of infinity. Stephen Hawking agreed with them when he described his "Grand Central Station" of the universe (the ever-"turning unity"), with its frozen clock of time hanging in its center. All of them in fact describing the same thing in their different ways.

    Dare I say it. The absolutely perfect definition and description of an evenly spread, uniform, "perpetual motion machine."
    Edwin Hubble For The Entirety Of His Life Said): 'If You Are Believing That My {Cosmological} "Redshift" Discovery Is Doppler Redshift Than You Are Reading TOO MUCH INTO MY {Cosmological} Redshift Discovery!!"
    Which, By The Way, Is An Excellent Baramoter For Determining How Far The Galaxy Or Star Was When That Galaxy Or Star Emitted The Light!!
    What Edwin Hubble Said For The Entirety Of His Life Was And Is That The Big Bang "Singularity" Perpetual Energy Machine Accelerating Universe): Never Could Have Happened And Never Did Happen Because His Discover The Cosmological Redshift IS NOT DOPPLER REDSHIFT!!
    Reply
  • Adoni Yannop
    Ryan F. Mercer said:
    You sound remarkably unknowledgeable about the scientific subject matter and the many empirical studies and experiments that underpin it. But you do you.
    Both Dark Matter Gravity And Dark Energy Are Real Actual Physical Constructs BUTTE Not As Given The DiPole RePeller Void Discovered In 2017 Exhibits Observable Dark Energy Expansion Of Its Space Even Going As Far As To Push Our Local Galactic Group And The Whole Of The Virgo Supercluster Towards The Norma Cluster At 290 km/s As The Shapley Attractor And The Great Attractor Pull Us At 341 km/s Towards The Overdensity Attractors For A Net Given Peculier Velocity Of 631 km/s.
    The Main Point Here Is That As Galactic Attractor Group Matter Heats Up, Matter Gravity And Dark Matter Gravity Are Generated Causing The Galactic Attractors To Crunch!!
    And That As Galactic Matter Cools In Voids, DiPole RePeller Voids Are Given To Expand!!
    Just As On Earth Radiant Heating Of Matter At The Equator Causes Low GP1 Aether Particle Pressure Causing Low Air Pressure Huricanes To Form While At Earth's Poles Matter Cooling Causes High GP1 Aether Particle Pressure Resulting In High Air Pressure Systems!!
    The Bottom Line Is That As Matter Heats Up And Generates Gravity); The Matter Particles Store Dark Energy That Comes Out As The Matter Particles Cool Conserving Energy Versus The Absurd Perpetual Energy "Singularity" Accelerating Expanding Universe Given As The Maker Of Heaven And Earth And Of All Things Visible!!
    The Fact Is That Indestructible Neutron Permeable Sacs That Decay To Indestructible Proton And Electron Permeable Sacs Evolved Over Infinite Time From God Particle 1 (GP1) Gaseous Aether Particles About A Quadrillionth The Mass Of The Electron In Our Ageless Finite In Volume Universe!!
    Reply
  • Adoni Yannop
    mbee1 said:
    More malarkey pretending to be knowledge. Dark matter and dark energy are math constructs, nobody has ever been able to verify either. The counting of clusters does not actually prove anything especially as they have a hole of about a third in the data, 3 billion years worth of hole. 500 clusters in a volume of space with an estimated diameter of 93 billion light years is a very low number. All that is a math construct based on background radiation assumed to have been lowered in frequency as space expanded. Nobody has actually found proof of what gravity is either. The Cern claims are just that claims. The whole expansion of space idea is simply a math construct, nobody actually knows it that is true either. You cannot see to the other side to see if there is another side. The big boom construct requires a force to expand space and hence the search for dark energy and due to some limited data on relative star movements dark matter if one simply ignores dark holes which may or may not radiate themselves away, nobody knows that either. If one assumes they do not than the number of black holes may be pretty large. None luminous matter may be much larger than known as well. Most of what passes for knowledge is actually educated guesses with nice math ribbons which may or may not be true. My point is take it all with a grain of salt and wonder at how it all came to be.
    Both Dark Matter Gravity And Dark Energy Are Real Actual Physical Constructs BUTTE Not As Given!!
    The DiPole RePeller Void Discovered In 2017 Exhibits Observable Dark Energy Expansion Of Its Space Even Going As Far As To Push Our Local Galactic Group And The Whole Of The Virgo Supercluster Towards The Norma Cluster At 290 km/s As The Shapley Attractor And The Great Attractor Pull Us At 341 km/s Towards The Overdensity Attractors For A Net Given Peculier Velocity Of 631 km/s.
    The Main Point Here Is That As Galactic Attractor Group Matter Heats Up, Matter Gravity And Dark Matter Gravity Are Generated Causing The Galactic Attractors To Crunch!!
    And That As Galactic Matter Cools In Voids, DiPole RePeller Voids Are Given To Expand!!
    Just As On Earth Radiant Heating Of Matter At The Equator Causes Low GP1 Aether Particle Pressure Causing Low Air Pressure Huricanes To Form While At Earth's Poles Matter Cooling Causes High GP1 Aether Particle Pressure Resulting In High Air Pressure Systems!!
    The Bottom Line Is That As Matter Heats Up And Generates Gravity); The Matter Particles Store Dark Energy That Comes Out As The Matter Particles Cool Conserving Energy Versus The Absurd Perpetual Energy "Singularity" Accelerating Expanding Universe Given As The Maker Of Heaven And Earth And Of All Things Visible!!
    The Fact Is That Indestructible Neutron Permeable Sacs That Decay To Indestructible Proton And Electron Permeable Sacs Evolved Over Infinite Time From God Particle 1 (GP1) Gaseous Aether Particles Defined As About A Quadrillionth The Mass Of The Electron In Our Ageless Finite In Volume Universe!!
    And Defined As The Medium Of Both Electromagnetic Waves And Gravitational Waves); And As The Building Block Of All Matter And Energy!!
    Reply